The present invention concerns a valve for use in high-performance liquid chromatography having a ball and a stricture that may be closed by the ball such that a fluid will be constrained from flowing through the valve.
In high-performance liquid chromatography (HPLC), a liquid must be propelled at typically very stringently controlled flow rates varying from, e.g., nanoliters/min. to milliliters/min., and high pressures typically falling within the range 20-100 MPa (200-1,000 bar) and beyond, and currently extending up to around 200 MPa (2,000 bar), where the compressibility of the liquid involved becomes evident. Liquid separation in an HPLC system involves forcing a mobile phase that, during operation, comprises a sample liquid containing components that are to be separated, through a stationary phase, such as a chromatographic column, in order to separate the various components of the sample liquid.
A serial arrangement of a pair of pumps for continuously propelling a liquid into an HPLC system is known from EP 0309596 A1. An outlet valve is situated between the primary pump and secondary pump in order to provide both that the primary pump will be unable to propel liquid into the system until the system pressure has been reached and that the secondary pump will pump liquid into the system, but not back into the primary pump.
Valves, such as outlet and/or inlet valves, are typically configured as passive check valves, where a ball is pressed against the spherical seat by the system pressure, i.e., by the pressure dropping across the ball, in order to constrain a fluid from flowing through the valve, where the ball is capable of moving in the axial direction and being lifted off the spherical seat in order to allow the fluid to flow through the valve. Active valves may also be similarly configured and employed as check valves.
Check valves are sufficiently well known from the state of the art and described in, among others, U.S. Pat. No. 4,945,945 A, U.S. Pat. No. 4,974,628 A, US 2009/104083 A1, DE 202006018959 U1, JP 2000283309 A, JP 2005133850 A, or JP 2006214539 A. A valve seat for high-pressure pumps, in particular, a valve seat for handling pressures exceeding 2,000 bar, is known from DE 3111614 A1.